Decommissioning a Role Instance
If necessary, you can safely remove a role instance such as a DataNode from a cluster while it is running by decommissioning the role instance. When you decommission a role instance, Cloudera Manager performs a procedure for you to safely retire the node on a schedule to avoid data loss. Role decommissioning applies to HDFS DataNodes, MapReduce TaskTrackers, YARN NodeManagers, and HBase RegionServers.
A role will be decommissioned if its host is decommissioned. In that case, the role will appear as decommissioned on the role instances page for the service. You can recommission the role from this page but the host will need to be recommissioned before any roles that were running on it can be restarted. See Decommissioning a Host for more details.
To decommission a role instance:
- Under the Services tab, click the link for the HDFS, MapReduce, YARN, or HBase service that contains the role instance you want to decommission.
- Click the Instances tab.
- Select the role instance(s) you want to decommission (such as a DataNode instance).
- From the Actions on Selected menu, select Decommission, and then click Decommission again to start the process. When you see a Finished status, the decommissioning process has finished.
To recommission a role instance:
- Under the Instances tab, select the decommissioned role instance(s) you want to recommission.
- From the Actions on Selected menu, select Recommission, and then click Recommission again to start the process. When you see a Finished status, the recommissioning process has finished.
If the host for this role instance is currently decommissioned, you will not be able to start this role until the host has been recommissioned.